86 Prof. Faraday on some Points of Magnetic Philosophy. 



round masses), and that the known experimental difference on 

 the opposite sides of these currents, shown by attraction and 

 repulsion of other currents, constitutes polarity. Ampere's 

 view is modified (chiefly by addition) in various ways by Weber, 

 De la Rive, Matteucci, and others. My view of polarity is 

 founded upon the character in direction of the force itself, what- 

 ever the cause of that force may be, and asserts that when an 

 electro-conducting body moving in a constant direction near or 

 between bodies acting magnetically on themselves or each other, 

 has a current in a constant direction produced in it, the mag- 

 netic polarity is the same ; if the motion or the current be 

 reversed, the contrary polarity is indicated. The indication is 

 true either for the exterior or the interior of magnetic bodies 

 whenever the electric current is produced, and depends upon the 

 unknown but essential dual or antithetical nature of the force 

 which we call magnetism (3154.). 



3308. The numerous meanings of the term polarity, and 

 various interpretations of polarity indications at present current, 

 show the increasing uncertainty of the idea and the word itself. 

 Some consider that the mere set or attraction, or even repulsion, 

 shown by a body when subject to a dominant magnet is sufficient 

 to mark polarity, and I think it is as good a test as any more 

 refined arrangement (2693.) when the old notion of polarity only 

 is under consideration. Others require that two bodies under 

 the power of a dominant magnet should by their actions show a 

 mutual relation to each other before they can be considered as 

 polar. Tyndall, without meaning to include any idea of the 

 nature of the magnetic force, takes his type from soft iron, and 

 considers that any body presenting the like or the antithetical 

 phaenomena which such iron would present under magnetic action, 

 is in a like or antithetical state of polarity*. Thomson does not 

 view two bodies which present these antithetical positions or 

 phsenomena as being necessarily the reverse of each other in 

 what may be called their polar states t, but, I think, looks more 

 to differential action, and in that approaches towards the views 

 held generally by E. Becquerel and myself. Matteucci considers 

 that the whole mass of the polar body ought to be in dependence 

 by its particles as a mass of iron is, and that a solution of iron 

 and certain salts of iron have not poles, properly speaking, but 

 that at the nearest points to the dominant pole there is the con- 

 trary magnetism to that of the pole, surrounded by the same 

 magnetism as of the pole in the further part, the two ends of a 

 bar of such matter between two dominant poles having no rela- 



* Athenseum, No. 1406, p. 1203. 

 t Ibid, column 3 at bottom. 



